MCQ
The $pK_a$ of weak acid $HA$ is $4.5$. The $pOH$ of an aqueous buffered solution of $HA$ in which $50\%$ of the $HA$ acid is ionised is
- A$4.5$
- B$2.5$
- ✓$9.5$
- D$7$
$pKa =4.5$
[Conjugate base $]=[$ acid], as $50 \,\%$ ionification
$pH =4.5+\log \frac{0.5}{0.5}$
$pH =4.5$
Then, $pOH =14-4.5=9.5$
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$Cr{(OH)_3} + Cl{O^ - } + O{H^ - } \to CrO_4^{2 - } + C{l^ - } + {H_2}O$
$Cr{(OH)_3}$ $-$ $Cl{O^ - }$ - $CrO_4^{2 - }$ $-$ $Cl^-$
Statement $I$ : The correct order of first ionization enthalpy values of $\mathrm{Li}, \mathrm{Na}, \mathrm{F}$ and $\mathrm{Cl}$ is $\mathrm{Na}<\mathrm{Li}<\mathrm{Cl}<\mathrm{F}$.
Statement $II$ : The correct order of negative electron gain enthalpy values of $\mathrm{Li}, \mathrm{Na}, \mathrm{F}$ and $\mathrm{Cl}$ is $\mathrm{Na}<\mathrm{Li}<\mathrm{F}<\mathrm{Cl}$
In the light of the above statements, choose the correct answer from the options given below :